The invention relates to a dishwasher, especially a domestic dishwasher with a washing compartment and apparatuses for washing tableware using washing liquor, wherein it is possible to set the pressure in the apparatuses for washing tableware. The invention further relates to a method for operating a dishwasher in which, in a washing program section in which washing liquor is applied to the tableware, the pressure in the apparatuses for washing tableware is varied.
Such a dishwasher is known for example from US 2004/0079400 A1. This discloses a dishwasher in which the operating state of a pump is controlled as a reaction to the turbidity of the washing liquor determined by a sensor. In this case the volume and/or the pressure of the washing liquor which is applied to the tableware to be washed are varied as a function of the turbidity of the washing liquor. The pump is configured in such cases to assume a plurality of operating states, with which different flow rates of the washing liquor can be set at the pump output.
A rerouting device for influencing the directional characteristic of the hydraulic arrangement and the circulating pump in order to allow a greater variation in the application of the washing liquor to the tableware is described in DE 101 63 184 A1. The characteristic of the hydraulic arrangement is changed by varying the flow of washing liquor through the rerouting device and the directional characteristic of the circulating pump by controlling the speed of the circulating pump.
A dishwasher in which the tableware held in the dishwasher is especially able to be cleaned as a function of the sensitivity and/or of the type and/or the intensity of the soiling, is described in DE 198 12 231 A1. In this device the speed of a motor of a circulating pump is able to be set. By setting the speed the pressure of the washing liquor can be varied over a wide range. In this case a delicate items program is provided in which the pump motor runs at a lower speed, and which can be selected when delicate items of tableware are held in the dishwasher. By contrast an intensive program is provided in which the pump motor runs at a high speed and which can be selected when heavily-soiled items of tableware are to be cleaned. Optionally the pressure can be controlled by means of valves in the supply pipes to the upper and lower basket.
Finally a domestic washing appliance is known from DE 199 51 839 A1 in which the speed of the circulating pump is influenced by a control device. In this case a turbidity sensor arranged in the domestic appliance monitors the cleaning liquid and issues a sensor signal to the control device. The speed of the circulating pump is set on the basis of this sensor signal. The pump speed is regulated in order to set a necessary volume of liquid in the pump sump, so that no air is sucked in through the pump.
The common aim underlying the prior art dishwashers described was to provide dishwashers with the lowest possible water consumption. This is brought about by setting the pressure in the apparatuses for washing the tableware, with the turbidity of the circulated washing liquor being included as a parameter for setting the pressure.